Wafer bonding for integrated optics
Physics of wafer bonding
Glass frit bondingGlass frit a slurry of fine glass particles in an appropriate carrierliquid Full sheet deposition or applied by screen printing Slurry heated to melt the glass particles Bonding upon solidification
Anodic bonding
Metallic bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Molecular wafer bonding
Surface cleaning
Surface cleaning
How to get rid of these particles?
Surface cleaning
Molecular wafer bonding
Surface activation
Surface activation
Deposited SiO2 allows to bond anything to anything
Surface activation
Molecular wafer bonding
Room temperature attachment
Molecular wafer bonding
Annealing
Annealing
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive wafer bonding
Adhesive bonding
Why adhesive die to wafer bonding? Less stringent requirements on surface quality
Micro-roughness Particle contamination Other types of contamination
Low temperature bonding process Planarization of SOI topography by spin coating
DVS-BCB adhesive bonding
Why DVS-BCB as a bonding agent? Low temperature bonding process (Tbond=250C) Very good planarization properties High glass transition temperature (Tg> 350C) High resistance against chemicals Known material in IC industry (packaging)
DVS-BCB adhesive bondingChemical formula
Commercially formulated by DOW as a B-staged oligomersolution (35% pre-polymerized)
By spin-coating: layer thicknesses of 1m to 25m available For our application: much thinner bonding layers are required
Dilution of the commercially available DVS-BCB using mesitylene
Stable spin coating of layer thicknesses down to 30nm
Si
CH3
CH3
Si
CH3
CH3
O
1,3-divinyl-1,1,3,3-tetramethyldisiloxane-bisbenzocyclobutene
DVS-BCB adhesive bondingOverview of the bonding process
Si-substrate
SiO2Si
BCB BCB BCB
BCB coatingWafer cleaning
Solvent evap + prepolymerization
Die attachment
BCB
BCB curing (pressurized)
DVS-BCB adhesive bondingCleaning of the SOI wafer surface using Piranha clean Standard Clean - 1 solution Standard Clean 2 solution
Particle free hydrophilic surface
Cleaning of the InP/InGaAsP die surface by Sacrifical removal of an InP epitaxial layer using 3HCl:H2O Sacrificial removal of an InGaAs layer using H3PO4:3H2O2:H2O
Particle free hydrophilic surface
DVS-BCB adhesive bondingPlanarization properties
Double spin coating has higher DOP than single coating with the same aggregate thicknessCuring profile and density of topography important for DOP
DVS-BCB adhesive bondingDie attachment process
Aligned attachment of dies and structured SOI wafer to carrier wafers
DVS-BCB adhesive bondingDie attachment process
Mounting of the carrier wafers in bonding chamber (carrier wafers are mechanically aligned)
DVS-BCB adhesive bondingDie attachment process
Evacuation of bonding chamber and attachment of dies (150C)
DVS-BCB adhesive bondingDie attachment process
Purging of the bonding chamber evaporation or release of temporary adhesive
DVS-BCB adhesive bonding
Equipment
Bonding equipment
Bonding equipment
Characterization equipment
Characterization Equipment
Characterization Equipment
Substrate removal
Bonding equipment
Unprocessed opto-electronic layer structure
Processed SOI waveguide wafer
Die to wafer bonding Substrate removal
Processing (definition of the component)
CMOS wafer
Photonic layer
Bonding of InP/InGaAsP dies and device processing
Bonding unprocessed dies using pick and place lowers needed alignment accuracy increases throughput
After die to wafer bonding all processing steps are wafer scale processes
Fabrication of bonded devices Photodetectors
Surface illuminated photodetector
Fabrication of bonded devicesPhotodetectors
Evanescently coupled MSM photodetectors
Fabrication of bonded devicesPhotodetectors and laser diodes
Inverted adiabatic taper approach Processing of both laser diodes and photodetectors identical
InP Microdisk Laser on Silicon
Multi-wavelength Laser on Si
III-V Photodetectors on Silicon
III-V Photodetectors on Silicon
Nonlinear ring resonators
Conclusions
Wafer bonding and die-to-wafer bondingtechnology is a very versatile technology with awide range of applicationsMolecular and adhesive (die-to-) wafer bondingare enabling technologies to realize complexphotonic integrated circuitsFuture research: to scale up the integration density todemonstrate the feasibility of complexactive/passive photonic integrated circuits